To properly drain the 3500 acres at MSP and the increased runoff from the new runway and appurtenances, the storm sewer system needed to be significantly upgraded. An entirely new trunk storm sewer system was developed on the west and south side of MSP, while the existing storm sewers were connected into the new ponds.

The new storm sewer system consists of several miles of sewer ranging from pipes as small as 18 inch diameter up to 10' by 10' box sewers. The storm water drains into a series of large holding ponds where water quality is monitored. The ponds cover over 14 acres of surface area. In cooperation with the Minnesota Department of Transportation, a third pond was constructed to hold drainage from Interstate 494.

Two 10-foot diameter tunnels carry surface water from the ponds underneath Highway 5, to the Minnesota River just east of the airport. The tunnels were built about 70-feet below the roadway elevation. The storm water drops more than 100 feet from inlet to outlet through this system. Concrete outfall structures were constructed on the outlet side of the tunnels to direct and slow water flow. The total cost of the storm sewer system is over $36 million.

Additionally, upgraded airfield culverts will be installed near Fort Snelling to take drainage from the northeast section of the airfield to Snelling Lake in 2006.